I keep waiting an answer from GS (I wrote to the technical support) ... but in the meantime I found a solution to my annoying problem ...
I found that famous registry key under HKEY_CURRENT_USER\Software\Graphisoft\ArchiCAD-64\ArchiCAD-64 16.0.0 ITA R1\3D selection
ENABLE HIDDEN SELECTION
I put the value to 0 (previous value was 1) and I also adjusted the other parameters HIDDEN LINE ALPHA, HIDDEN POINT ALPHA and IMPORTANT HIDDEN LINE ALPHA to 1500 (after several attempts) and my multiple selection is much much faster and more precise than before.
I got this result because (changing the values above) I probably excluded the hidden entities behind the ones directly visible in the scene.
Maybe these features regarding the selection of hidden objects are not fully implemented in my hardware (nVidia Quadro FX 1700) which is not so new (2008) ... Probably the new videocards implement directly these instructions and are faster
AC27 latest hotfix
Win 10 Pro 64bit
Double XEON 14 CORES (tot 28 physical cores)
32GB RAM - SSD 256GB - Nvidia Quadro K620
Display DELL 25'' 2560x1440
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